Add NodeGit versions to docs

Author: John Haley

_config.yml

@@ -3,9 +3,13 @@ title: NodeGit
 description: Asynchronous native Node bindings to libgit2
 url: "http://nodegit.org"
 date_format: "ordinal"
-current_nodegit_version: 0.5.0
+current_nodegit_version: 0.6.3
 other_nodegit_versions:
   - HEAD
+  - 0.6.2
+  - 0.6.1
+  - 0.6.0
+  - 0.5.0
   - 0.4.1
   - 0.4.0
   - 0.3.3